深入Java设计模式之适配器模式

适配器模式概念

适配器模式(Adapter Pattern)：将一个接口转换成客户希望的另一个接口，使接口不兼容的那些类可以一起工作，其别名为包装器(Wrapper)。适配器模式既可以作为类结构型模式，也可以作为对象结构型模式。

在适配器模式中，我们通过增加一个新的适配器类来解决接口不兼容的问题，使得原本没有任何关系的类可以协同工作。

根据适配器类与适配者类的关系不同，适配器模式可分为对象适配器和类适配器两种，在对象适配器模式中，适配器与适配者之间是关联关系；在类适配器模式中，适配器与适配者之间是继承（或实现）关系。
 

类适配器实际应用 

Customer期望能通过调用AddressValidator接口isValidAddress方法，从而实现调用USAddress/CAAddress类的验证方法(实现不同验证器的统一调度)。
CAAddress是原来老系统里就存在的类,不能把方法名isValidCanadianAddress直接改为isValidAddress。否者会影响老系统的使用
这时就需要一个适配器CAAddressAdapter继承CAAddress，并且实现接口isValidAddress
Customer的里根据入参来判断是实例化CAAddressAdapter还是USAddress 

package com.lzhsite.technology.designPattern.adapter.Address;

public class Customer
{
    public static final String US = "US";
    public static final String CANADA = "CANADA";

    private String address;
    private String name;
    private String zip;
    private String state;
    private String type;

    public Customer(String address, String name, String zip, String state, String type)
    {
        this.address = address;
        this.name = name;
        this.zip = zip;
        this.state = state;
        this.type = type;
    }

    public boolean isValidAddress()
    {
    	//Customer期望能通过调用AddressValidator接口isValidAddress方法，从而实现调用USAddress/CAAddress类的验证方法(实现不同验证器的统一调度)。
        //CAAddress是原来老系统里就存在的类,不能把方法名isValidCanadianAddress直接改为isValidAddress。否者会影响老系统的使用
    	//这时就需要一个适配器CAAddressAdapter继承CAAddress，并且实现接口isValidAddress
    	//Customer的里根据入参来判断是实例化CAAddressAdapter还是USAddress
    	AddressValidator addressValidator = getValidator(type);
        return addressValidator.isValidAddress(address, zip, state);
    }

    private AddressValidator getValidator(String customerType)
    {
        AddressValidator addressValidator = null;
        if (customerType.equals(Customer.US))
        {
            addressValidator = new USAddress();
        }
        if (customerType.equals(Customer.CANADA))
        {
            addressValidator = new CAAddressAdapter();
        }
        return addressValidator;
    }
}

package com.lzhsite.technology.designPattern.adapter.Address;

public class USAddress implements AddressValidator
{
    public boolean isValidAddress(String address, String zip, String state)
    {
        if (address.trim().length() < 10)
        {
            return false;
        }
        if (zip.trim().length() < 5 || zip.trim().length() > 10)
        {
            return false;
        }
        if (state.trim().length() != 2)
        {
            return false;
        }
        return true;
    }
}

package com.lzhsite.technology.designPattern.adapter.Address;

public class CAAddressAdapter extends CAAddress implements AddressValidator
{
    public boolean isValidAddress(String address, String zip, String state)
    {
        return isValidCanadianAddress(address, zip, state);
    }
}

package com.lzhsite.technology.designPattern.adapter.Address;

public class CAAddress
{
    public boolean isValidCanadianAddress(String address, String pcode, String prvnc)
    {
        if (address.trim().length() < 15)
        {
            return false;
        }
        if (pcode.trim().length() != 6)
        {
            return false;
        }
        if (prvnc.trim().length() < 6)
        {
            return false;
        }
        return true;
    }
}

 

package com.lzhsite.technology.designPattern.adapter.Address;

public class CAAddress
{
    public boolean isValidCanadianAddress(String address, String pcode, String prvnc)
    {
        if (address.trim().length() < 15)
        {
            return false;
        }
        if (pcode.trim().length() != 6)
        {
            return false;
        }
        if (prvnc.trim().length() < 6)
        {
            return false;
        }
        return true;
    }
}

适配器模式的总结

完整代码

https://gitee.com/lzhcode/maven-parent/tree/master/lzh-technology/src/main/java/com/lzhsite/technology/designPattern/adapter